Measuring ultra-large scale effects in the presence of 21cm intensity mapping foregrounds

Abstract

\textsc{Hi} intensity mapping will provide maps of the large-scale distribution of neutral hydrogen (\textsc{Hi}) in the universe. These are prime candidates to be used to constrain primordial non-Gaussianity using the Large Scale Structure of the Universe as well as to provide further tests of Einstein's theory of Gravity (GR). But \textsc{Hi} maps are contaminated by foregrounds, which can be several orders of magnitude above the cosmological signal. Here we quantify how degenerated are the large-scale effects ($f_{\mathrm{NL}}$ and GR effects) with the residual foregrounds. We conclude that a joint analysis does not provide a catastrophic degradation of constraints and provides a framework to determine the marginal errors of large scale-effects in the presence of foregrounds. Similarly, we conclude that the macroscopical properties of the foregrounds can be measured with high precision. Notwithstanding, such results are highly dependent on accurate forward modelling of the foregrounds, which incorrectly done catastrophically bias the best fit values of cosmological parameters, foreground parameterisations, and large-scale effects.

14 pages, 5 figures, 4 tables. Agrees with published version

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Cited by in corpus (10)

• SKAO HI Intensity Mapping: Blind Foreground Subtraction Challenge
• The foreground transfer function for HI intensity mapping signal reconstruction: MeerKLASS and precision cosmology applications
• Detecting the power spectrum turnover with HI intensity mapping
• Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
• The local PNG bias of neutral Hydrogen, ${\mathrm{H}}_{\mathrm{I}}$
• Multi-wavelength spectroscopic probes: biases from neglecting light-cone effects
• Anti-symmetric clustering signals in the observed power spectrum
• A Multi-messenger view of Cosmic Dawn: Conquering the Final Frontier
• Foreground removal in HI 21 cm intensity mapping under frequency-dependent beam distortions
• Multi-wavelength spectroscopic probes: prospects for primordial non-Gaussianity and relativistic effects